Radiofrequency (RF) electronics components, such as power amplifiers, low-noise amplifiers, filters, switches, power management modules, tuners, and sensors, provided on integrated circuits and for use in wireless communication systems such as smartphones are prevalent in current technology. Many such components include a control interface usable for controlling operation of the components. One such control interface is the RF Front-End (RFFE) Control Interface as specified by the MIPI™ Alliance. The RFFE is a standard three-pin control interface which currently supports a master and up to 15 slave devices per bus, with a master capable of hosting more than one bus. Slave devices on a common bus may be addressed using one of 15 different possible addresses, referred to herein as Unique Slave Identifier (USID) addresses. A standard implementation for full USID address configurability of a slave device would require four input pins for setting the device's address register, for example via pull-up and/or pull-down resistors. However, the incorporation of four address pins in a chip device is problematic due to device size and cost constraints. As such, not all RFFE compatible devices are configurable to the full range of USID addresses. Rather, it is common for devices to have fixed USID addresses or limited configurability thereof.
Integrated circuit inputs settable by pull-up and/or pull-down resistors are commonly used in the electronics industry. Such inputs may be associated with a digital state of the integrated circuit, for example via an input register. However, the incorporation of a separate, dedicated pin for setting each register individually is again problematic due to device size and cost constraints.
U.S. Pat. No. 5,532,655 discloses a method for using the same input/output pin on an integrated circuit for both a high frequency AC signal and a DC signal simultaneously and a first circuit means to accomplish this multiplexing. According to U.S. Pat. No. 5,532,655, the circuit topology comprises a first and second capacitor, coupled between the AC signal input and the AC signal output. A first and second resistor are coupled to the same input/output pin as the capacitors but between the two capacitors and respectively to a DC signal input and a DC signal output. The DC signal path thus lies between the two capacitors and sees them as open circuits, while the AC signal path sees the two resistors as open circuits and the capacitors as short circuits. However, U.S. Pat. No. 5,532,655 is limited in its disclosure and subject to improvement, for example with respect to applicability to setting of address registers of RFFE devices.
Therefore there is a need for a method and apparatus and system for register setting via multiplexed chip contacts that is not subject to one or more limitations of the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.